I would think a hoax by a small film maker whoring for attention or someone shy of the camera back then are a more likely answer than time travelers walking into cameo shots with out-of-period artifacts.

One thing that immediately pops into my mind: If this would be a time traveler, than this has to be something far more advanced than today's mobile phones, or did the time travelers bring with them (and set up) all the infrastructure as well?

So this "proves", that we do not see a time traveler using a mobile phone